DETROIT — Nine Catholic nuns in southern Michigan have died in January due to a COVID-19 outbreak at their retirement home, which had gone for months without a single case, officials said Thursday.

The women lived at the campus of the Adrian Dominican Sisters in Adrian, 75 miles southwest of Detroit. They had been teachers, nurses and pastoral ministers before retiring to a life of “prayer and presence,” said Sister Patricia Siemen, leader of the religious order.

“Of course, our hearts are breaking,” she said.

“We’re grieving, but we also know that we are not alone in this,” Siemen told The Associated Press. “We are not alone in the suffering of the world.”

COVID-19 has been cited in the deaths of dozens of retired or infirm nuns who lived in congregate settings in the U.S. Eight nuns in suburban Milwaukee died of virus complications in one week in December, including four in one day.

Twelve Adrian Dominican nuns have died in January, including nine because of COVID-19, Siemen said. They ranged in age from 79 to 97. The latest was Sister Helen Laier on Tuesday.

Siemen said many had other health problems that were exacerbated by the virus.

After more than nine months without a COVID-19 case among residents, the Adrian Dominican Sisters announced an outbreak on Jan. 14. It said “stringent protocols,” including quarantines, were being followed.

Forty-six sisters have tested positive, 12 cases remain active and 25 women are recovering, spokeswoman Angela Kessler said. More than 200 sisters who are retired from active ministry live in Adrian.

“It slips in. That’s the heartache of this virus,” Siemen said. “We’ve had no guests on campus. Our sisters have not seen their family members. They haven’t even seen our other sisters who live off campus since this started in the middle of March. And yet that virus is very sneaky.”

Residents received the first dose of the Moderna vaccine on Jan. 15, along with more than 50 employees, Kessler said.

Adrian is the headquarters for the global religious group, which has more than 500 sisters and a presence in 22 states as well as four countries outside the U.S. It founded Siena Heights University in Adrian.